Jet engine exhaust nozzle limiting mechanism



Feb. 2, 1960 2,923,127

JET ENGINE EXHAUST NozzLE LIMITING MECHANISM R. E. BIEHL. ETAL Filed Sept. l0, 1957 E E A INILQ: who, Fw

United States Patent O JET ENGINE EXHAUST NOZZLE LIMITING MECHANISM Richard E. Biehl, Pearl River, and Elia A. Gallo, Englewood, NJ., assignors to Curtiss-Wright Corporation, a corporation of Delaware Application September 10, 1957, Serial No. 683,171

8 Claims. (Cl. 60`-35.6)

This invention relates .to the exhaust nozzle of a jet engine and is particularly directed to such exhaust nozzles of the convergent-divergent type having means for varying the nozzle throatvand exit areas.

In the case of a jet engine convergent-divergent nozzle having a variable nozzle throat and a variable nozzle exit area, the range of adjustment of thenozzle exit area depends on the adjustment of the nozzle throat area. Thus for each position of the nozzle throat area, the nozzle exit area should not be closed more than the nozzle throat and in addition the nozzle apparatus will impose limits as to how far the nozzle exit area can be opened without physical damage to parts of the nozzle. Hence, for each position of the nozzle throat there are limits dening the permissible range of adjustment of the nozzle exit area.

An object of the present invention comprises the provision of simple and novel means for automatically limiting adjustment of the nozzle exit area within limits determine-d by the adjustment of the nozzle throat area.

Other objects of the invention will become apparent upon reading the annexed detailed description in connection with the drawing in which: l

Fig. l is a schematic view of a nozzle embodying the invention; and

Fig. 2 is a sectional View taken along line 2 2 of Fig. 1.

Referring to the drawing reference numeral 10 designates a portion of the exhaust duct of a jet engine. A variable area convergent-divergent nozzle 12 is mounted at the discharge end of said duct. As illustrated, Vthe nozzle 12 comprises a plurality of circumferentially overlappingupstream nozzle members 14 which are hingedly supported at their upstream ends at the discharge end of the duct 10. In addition the'nozzle 12 includes a plurality of circumferentially overlapping downstream nozzle members 16 which are hingedly connected at their upstream ends to the downstream ends o-f the nozzle members 14. A hydraulic motor 18 is mounted on a support bracket 20 which is secured to the duct 10 at a point spaced from the discharged end of said duct. The motor 18 includes al piston 22 slidable in a cylinder 24 and having a piston rod 26 connected to a ring 28 which in turn is connected to each of the upstream nozzle members 14 by links 29. Similarly a second hydraulic motor 30 is mounted on the duct 10. As illustrated the motor 30 is secured to the same bracket 20 as the motor 18. The motor 30 includes a cylinder 32 having a piston 34 slidable therein. A piston rod 36 connects the piston 34 to a ring 38 which in turn is connected as illustrated to the downstream nozzle members 16. With this construction by applying hydraulic pressure to one end of the motor 18 and venting the other end the upstream nozzle members can be adjusted to vary the cross-sectional area of the nozzle throat 40. Similarly the motor 30 is operable to adjust the downstream nozzle members to vary the cross-sectional area of the nozzle exit 42 independently of the nozzle throat.

At this point it should be noted that for the purpose of this description the words left and right refer to the apparatus of the invention as viewed in Fig. 1.

The hydraulic motor 18 for the nozzle throat may be controlled by any. suitable valve mechanism not shown. The hydraulic motor 30 for the nozzle exit is controlled by a servo valve 44. The valve 44 comprises a spooltype member which has a neutral position for closing the two passages 46 and 48 communicating with opposite ends of the cylinder 32 of the motor 30. Movement of the valve 44 to the left is effective to admit hydraulic pressure from a supply line 50 to the passage 46 and at the same time the passage 48 is vented whereupon the piston 34 of the motor 30 moves to the left to effect an opening adjustment of the downstream nozzle members 16 to increase the nozzle exit area 42. Similarly movement of the valve 44 in the opposite direction (to the right) is effective to apply hydraulic pressure to the piston 34 to move the piston to the right to effect a closing adjustment of the downstream nozzle members to decrease the nozzle exit area 42.

The servo valve 44 for controlling the nozzle exit area is connected to a suitable yieldable motor 52 which may form part of a control circuit. A suitable control circuit for this purpose is disclosed in copending application Serial No. 329,956 led January 7, 1953, now Patent No. 2,846,843.

As already stated for each adjustment of the nozzle throat 40 there are different physical limits for the adjustment of the nozzle exit area. These physical limits are indicated by the dot and dash lines 16a and 1Gb indicating the outer and inner limiting positions repectively for the downstream nozzle members 16. The mechanism l 54 is provided so that when the downstream nozzle members 16 are at one or the other of their limiting positions energization of the motor 30 in a direction to move said members beyond said limit is prevented.

The nozzle limiting mechanism 54 includes a housing 56 supported on the duct 10, for example on the bracket 20 and a rotatable shaft 58 is journaled in said housing. The shaft 58 is connected to the piston 34 by a flexible shaft 59 and a rack and pinion connection 60 lwith the piston rod 36 so that motion of the piston 34 results in rotation of the shaft 58. The shaft 58 is axially movable in the housing 56 and is located axially by centering springs 62.

The shaft 58 is connected to the servo valve 44 as indicated. For this purpose a pair of washers 66 are journaled on the shaft 58 on opposite sides of -a shoulder 68 on said shaft, bearing members 70 being interposed between said shaft and washers. Each washer 66 has an arm 72 with forked ends which straddle a shaft 74 connected to the servo valve 44 preferably through a slight loose fit indicated at 76. The washers 66 engage abutments 78 on the shaft 74 so that any axial motion of the shaft 58 is transmitted to the shaft 74. The washers 66 do not rotate but the bearings 70 between slalid washers and the shaft 58 permit rotation of said s aft.

A cam-like member 80 is pivotally supported in the housing 56 at 82 on a shaft-like member 84. The cam member 80 has a cut-out portion forming spaced camlike tracks 86 and 88. A nut 90 is threaded on the shaft 58, saidv nut having a projection or part 92 engageable with the cam-like tracks 86 and 88. As will become apparent the cam-like tracks 86 and 88 actually function as spaced abutments engageable by the projection 92 on the nut to limit axial motion of said nut along the shaft 58. The member 80 comprises two side by side plates as shown in Fig. 2 and the nut 90 has at sides fitted between said plates to prevent rotation of said nut.

The bearings 94 for the shaft 84 permit axial sliding 3,923,127V l ,f f'

motion of the shaft 84 relative to the housing 56. The i shaft 84y has a pair ofv l-ateral extensions 96 and 98 in which a shaft 100 is journaled. The shaft 58 extends freely through openings in said extensions 96 and 98 while theshaft 100L is provided with shoulders V1.02 which engage the extensionsA 96 and 98- so that the shafts 84 and 100 move axially-as a unit. Theshaft 84 is connected to the d uct 1-0 at the nozzle end of said.. duct by a bracket 1 04 supported at saidhduct end. The shaft 100 is connected to the piston 22 byn a ilexible shaft 1616 and a rack and pinion connection 108 `with the piston rod 26 so that motion ofthe piston 22 results in rotation ofthe shaftllltli Y A nutllil is threaded onI the yshaft 100; Thenut 110 is connected to the cam plates 80 by links 112, one end of eachv link 112 being pivotally connected tothe nut 11@ and the otherA end being pivotally connected to one of the cam plates 80. Thus the cam-like member 80 and shaft 100 are both connected to the discharge end of the duct fby the shaft 84 and bracket 104. As i s apparent in Fig. 2 the links 112 engage the sides of the nut 110 to prevent rotationfof said nut. A spring 114 is connected under tension between extensions 116 of the cam plates 80 and an extension 118 byA theshaft 84 to take up all looseness in the fit of the cam member 80 and associated parts.

The nozzle limitingmechanism 54 described operates as follows: When the servo piston 341moves to adjust the downstream nozzle members 16, the shaft 5,8 is rotated to cause the nut 90 to thread along said shaft between the cam tracksr86 and 88. LikewiseV when the servo piston 22 moves to adjust the upstream nozzle members 14, the shaft 100 is rotated whereupon the nut 110 is caused to thread along said shaft. This motion of the nut 110 is effective through the links 1712;"to swing the cam members Y8,0 about the pivot 82 thereby moving the cam tracks 86 and 88 relative to the projecting part 92 on Vthe nut 90. However as long as Vthe projection 92 on the nut 90 is out of contact with the abutments or cam-like tracks 86 and 88, the nozzle limiting mechanism has no ycontrol over the positions of the nozzle members 14 and 16 by the servo motors 18 and 30. i l

The arrangement is such that motion, of the piston 34 to the left to eifect an opening adjustment of the nozzle exit members 16 is effective vto rotate the shaft`58 in a direction to move `the nut 90gto the left along said shaft. When the projection 92 on the nut 90 engages the left cam track 86 the upstream nozzlel members 16 are at the outer limit 16a o-f their range of adjustment. If the control motor 52l should now urge the servo valve 44 in a direction (to the left) to admit hydraulic pressure Vto the line 46 for further moving the piston 34 in a nozzle exit opening direction (to the left), this motion of the piston would cause the shaft 58 to rotate in a direction urging the nut 90 further to the left along the shaft 58. However, since the nut projection 92v is now in engagement with the left cam 86v to prevent further motion of the nut to the left, this rotation of the shaft 58 relative to the nut 90 will cause saidl shaft to move axially to the right against vthe centering action of the springs 62.

l This axial motion of the shaft 58 tothe rightis transmitted to the siervo valve 44 to move said valve to the right toward or beyond ,its neutral position vtorprevent further opening adjustment of the nozzle exit members 16 or even to effect a closing adjustmentof said members.

Similarly motion of the piston 34 toward the right to effect a closing adjustment ofthe nozzle exit members 16 will cause the shaft 58V to rotate in aY direction to cause 4 tationof the shaft v58 will now cause said shaft to move toward the left against the centering action of the springs 62. This motion of the shaft-58 to the left will be transmitted to theservo valve to move said valve back toward or beyondits neutral position to prevent further closing adjustment'of the nozzle exit members 16 or even to effect an opening adjustment of *saidl members.

In the foregoing Vdiscussion of the operation of the limiting mechanism 54, the cam pivot 82 has beenconsidered fixed and the connection of the links 112 to the other end of the cam has been considered xed by its connection to the nut 110. However, motion ofthe piston 22 to adjust the nozzle members 14 for adjusting the nozzle throat V40V is eiective to rotate the shaft 100 to cause the nut 110 to move along said shaft. This motion of the nut 110 is transmitted to the cam 80 through the links 112 thereby pivotally swinging the vcam 80 about its pivot 82 to shift the abutments or cam tracks 86 and 88 and thereby shifting the limiting positions 16a and Y16b of the nozzle exit members 16.l The arrangement is such that-motion of the piston 22 for-example, to the right to effect an opening adjustment of the nozzle throat is eifective to cause the nut 110 to travel toward the left thereby shifting the abutments or camlike tracks 86 and 88- toward the left to-4 open eachof the limits of adjustment 16a and 16b of the nozzle exit members. If aty this time the nozzle exit members 16 were at'rtheir inner limit 16b the projection 92 would be in 'engagement with the abutment or cam track 88. Said shift of thefcarn tracks to the left would then be transmitted .to the shaft S8 through the projection 92 and thence to ,(16a-16b) ofthe nozzle exit members 16 in a closing direction.

The cam 80 is pivotedat 82 on the shaft ,84' rather than on the housing 56 to provide compensation for thermal expansion and contraction of the duct 10' relative to the piston rod 26 and rod 84. Since the rods 26 and 84 are both outside the duct 10, they will be at substantially the samer temperature. Expansion of the duct 10 relative to said piston rod 26 by itself will cause a closing adjustment of the nozzle throat 40. Hence, in

Y mal expansion.

such case, inv order to bring the nozzle throat to the desired value the piston 22 of the hydraulic motor 18 must be moved further to the right than it would otherwise have to be inthe absence of said differential ther- This means that the shaft 100 and its v nut 110 have pivotally swung the cam-like member 80 However,V said expansion of the duct 10 will also result in a differential motion between the housing 54 andthe the nut 90 to travel to the rightalong said shaft. When discharge end yof said duct. Since the cam pivot 82. and shaft are both connected to the' duct discharge end through the shaft 84 the cam-like member 80, supported on the shaft 84 iat the pivot 82 and on the shaft 100,

'will be given a compensating shift to the right relative to the shaft V58 and its nut 90 to compensate for the aforesaid shift ofY said ycam-like membery 80 tothe left bythe nut K4 as a result of' thermal expansion ofthe duct 1,07. Y Y

It is not essential that the housing 54 be supported kon the duct 10.at thesamepoint as the motor 18. since the arnounthof said temperature compensationrequired.l can bey adjusted by varyingthe moment arm of the 4point ofcontact ofthe projection 92 on the camflikegmern-ber 80. In addition the rods 26 and 84 can be made-,of nate rial having different temperature coeicients of expansion so as to provide the desired compensation.

The loose connection 76 is not essential to the invention. It has been provided so that in the normal control operation of the servo valve 44 by the motor 52, it is not necessary for the motor 52 to move the various parts of the limiting mechanism connected to said valve. At this point it should be noted that the actual range of movement of the servo valve 44 by the servo piston is quite small and may be only a few hundredths of an inch.

While we have described our invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding our invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. We aim in the appended claims to cover all such modifications.

We claim as our invention:

1. Mechanism for adjusting a convergent-divergent nozzle comprising means for adjusting the nozzle throat area; means for adjusting the nozzle exit area; means for limiting the adjustment of the nozzle exit area to a predetermined range; and means operatively connected to said nozzle throat area adjusting means for adjusting the limits of said range with adjustment of the nozzle throat area.

2. Mechanism for adjusting a convergent-divergent nozzle comprising means for adjusting the nozzle throat area; means for adjusting the nozzle exit area; a first member operatively connected to said nozzle throat area adjusting means for movement therewith; and a second member operatively connected to said nozzle exit area adjusting means for movement therewith, said members being engageable upon adjustment of said nozzle exit area adjusting means to the limits of a predetermined range of adjustment, determined by the position of said first member, for preventing adjustment of said nozzle exit area adjusting means beyond said range.

3. Mechanism for adjusting a convergent-divergent nozzle comprising means for adjusting the nozzle throat area; means for adjusting the nozzle exit area; a first member; a second member operatively connected to said nozzle exit area adjusting means and engageable with said first member to limit the adjustment of said nozzle exit area adjusting means to a predetermined range; and means operatively connecting said nozzle throat area adjusting means to said first member for adjusting the limits of said range in response to adjustment of the nozzle throat area adjusting means.

4. Mechanism for adjusting a convergent-divergent nozzle comprising iirst motor means for adjusting the nozzle throat area; second motor means for adjusting the nozzle exit area; a first member; a second member operatively connected to said second motor means and engageable with said first member at the limits of a predetermined range of adjustment of said second member; means operatively connected to said second member and effective upon said engagement of said first and second members for preventing operation of said second motor means in a direction for moving said second member beyond said range; and means operatively connecting said first motor means to said first member for adjusting the limits of said range in response to operation of said lirst motor means.

5. Mechanism for adjusting a convergent-divergent nozzle comprising first motor means for adjusting the nozzle throat area; second motor means for adjusting the nozzle exit area; servo valve means operable for controlling said second motor means; a first member; a

second member operatively connected to said second motor means and engageable with said first member at the limits of a predetermined range of adjustment of said second member; means operatively connecting said second member to said servo valve upon engagement of said iirst and second members to prevent energization of said second motor means in a direction for moving said second member beyond said range; and means operatively connecting said first motor means to said first member for adjusting the limits of said range in response to adjustment of said first motor means.

6. Mechanism for adjusting a convergent-divergent nozzle comprising means for adjusting the nozzle throat area; means for adjusting the nozzle exit area; a first member; a second member operatively connected to said nozzle exit area adjusting means, one of said members having a pair of spaced abutments and the other of said members having a part engageable with said spaced abutments at the limits of a predetermined range of adjustment of said second member for limiting adjustment of the nozzle exit area adjusting means to a predetermined range; and means operatively connecting said nozzle throat area adjusting means to said first member for adjusting the limits of said range in response to adjustment of the nozzle throat area adjusting means.

7. Mechanism for adjusting a convergent-divergent nozzle comprising first motor means for adjusting the nozzle throat area; second motor means for adjusting the nozzle exit area; servo valve means operable for controlling said second motor means; a first'member; a second member operatively connected to said second motor means, one of said members having a pair of spaced abutments and the other of said members having a part engageable with said spaced abutments at the limits of a predetermined range of adjustment of said second member; means operatively connecting said second member to said servo valve means upon occurrence of said abutment engagement to prevent energization of said second motor meansjin a direction for moving said second member beyond said range; and means operatively connecting said first motor means to said first member for adjusting the relative positions of said abutments and part to adjust the limits of said range in response to adjustment of said first motor means.

8. In combination with an exhaust duct for a jet engine having a variable area convergent-divergent nozzle at the discharge end of said duct; first motor means mounted on said duct at a point spaced from said nozzle and connected to said nozzle for adjusting the nozzle throat area; second motor means mounted on said duct and connected to said nozzle for adjusting the nozzle exit area; and mechanism for limiting the adjustment of the nozzle exit area; said mechanism comprising a first member connected to the discharge end of said duct for axial movements therewith in response to thermal expansion and contraction of said duct; a second member operatively connected to said second motor means and supported from said duct at a point spaced from said nozzle, said members having abutment means engageable to limit the operation of said second motor means to a predetermined range; and means operatively connecting said first motor means to said first member for adjusting the limits of said range in response to operation of said first motor means.

Anxionnaz et al. Oct. 9, 1951 Weiler et al. July 15, 1952 

